Covers for crops, primarily horticultural crops, are known, where the cover includes a framework of piping that carries a net for protecting the crops against insects and birds. Such covers are used in connection with high beds in gardens and their design is inspired by covers for greenhouses, where a framework of larger dimensions carries nets, glass panes or transparent plastic films.
The covers of high beds may typically be opened by loosening the net from the framework and lifting the net aside. However, exposing the entire high bed is often not expedient, particularly in case of large high beds, as exposing the whole high bed provides increased access for insects in the period of time where the cover is removed. It would be advantageous to suffice with lifting just a part of the net aside in order to provide access to a part of the bed.
Large greenhouses are also known with a cover of double plastic film. For example, in EP application 21 8 34 is disclosed a greenhouse where double-walled plastic films extend from the roof ridge and to the sides, and other plastic films extend down along the sides. The plastic films are fastened around poles placed in countersunk grooves, where the rail on the roof ridge is permanently fastened, while the rail at the sides is fastened by hook-like engagement with a bent rail. The principle is not intended for smaller units for horticultural use, and an entrance will traditionally be at the end of the greenhouse. A possible exposing of the sides may only take place by opening a whole side at a time, which is inexpedient. In addition, an unsuitable amount of force has to be used for releasing the flexible cover from the hook-like engagement.
Another type of greenhouse is described in EP 306 717. On a rod framework is provided inflatable double flexible covers which along their edges are fastened around rods provided in countersunk grooves in the framework. These double flexible covers are not intended to be loosened from the rods in order to access the crops. Different types of greenhouses are disclosed in WO01/04431, FR2679734, U.S. Pat. No. 2,986,150. None of these greenhouses comprise the possibility for using flexible covers having equal length without difficulties.
By greenhouses of glass, like in GB 2 172 040, it is known to provide the bottom side of the glass with canvases for screening against light. Access to the greenhouse traditionally occurs through a door. The system is an expensive traditional system and not suited for customers wanting a light and flexible system at a low cost.